Steroid signalling in the human ovarian surface epithelium wound healing

Abstract

The human ovarian surface epithelium (hOSE) is a cell monolayer that covers the surface of the ovary. Natural events like incessant ovulation, associated reproductive hormone action prior to and post-ovulation, along with the ovulationassociated inflammation, that result in injury and repair of hOSE, are considered to have a role in the development of epithelial ovarian cancer (EOC). Progesterone is apoptotic and anti-inflammatory, whereas androgens appear cytoproliferative for hOSE. Local generation of these steroid hormones is subject to 3β-hydroxysteroid dehydrogenase (3β-HSD) activity. Moreover, action of these hormones is achieved through coupling to their cognate receptors, progesterone (PR) and androgen receptors (AR). The overall aim of this thesis is to elucidate in vitro the regulation of progesterone and androgen biosynthesis and downstream signalling during the injury and repair of primary hOSE cells that were collected from pre-menopausal women who underwent surgery for benign gynaecological disorders. Injury was mimicked by treatment of cells with several pro-inflammatory cytokines, whereas repair was mimicked with T-lymphocyte, ‘anti-inflammatory’ cytokines. Immunohistochemical studies showed immunodetectable 3β-HSD in the human ovarian cell surface of whole ovary and three-week cultured hOSE cells, establishing 3β-HSD expression in vivo and in vitro. Cross-reaction of the 3β-HSD antibody with both enzyme isoforms did not allow investigation of isoform expression pattern. However, mRNA transcriptional studies with isoform specific primers and probe sets for semi-quantitative (sq) and quantitative (q) PCR revealed expression of both isoforms in hOSE cells; 3β-HSD1 mRNA was expressed at higher levels relative to 3β-HSD2 mRNA in accordance with the preference of this isoform in peripheral non-steroidogenic tissues. Of the cytokines tested, only IL-1α and IL-4 affected 3β-HSD expression. IL- 1α suppressed 3β-HSD1 mRNA, whereas it up-regulated 3β-HSD2 mRNA as assessed with qPCR, without though affecting total 3β-HSD protein and activity levels as assessed with western immunoblotting and radiometric activity assays, respectively. IL-1α did not affect AR or PR mRNA levels, suggesting a balance in androgen and progesterone biosynthesis during post-ovulatory wounding. IL-4 massively induced 3β-HSD1 and 3β-HSD2 mRNA and total 3β-HSD protein and activity. It also attenuated AR mRNA and protein, without affecting PR mRNA. Collectively, these data demonstrate that IL-4 sustains progesterone rather than androgen signalling and this may be part of the anti-inflammatory steroid action that protects hOSE from genetic damage. IL-1α effects appear to be mediated by NF-κB signalling pathway. PI-3K and p38 MAPK appeared involved in IL-1α-induced 3β- HSD2. IL-4-induced 3β-HSDs required STAT-6 and PI-3K pathways and also p38 MAPK at the case of 3β-HSD2. IL-4-attenuated AR was reversed by a p38 MAPK inhibitor. These data suggest that steroid signalling by IL-1α and IL-4 involve multiple signalling pathways. In primary EOC, 3β-HSD1 and 3β-HSD2 transcripts were attenuated relative to hOSE cells, suggestive of an acquired feature of neoplastic transformation. However, both transcripts could be restored after IL-4 treatment, attesting a therapeutic advantage of this cytokine. In conclusion, we have shown that 3β-HSD is under inflammatory control during ovarian post-ovulatory wound healing of hOSE. IL-1α- and IL-4-mediated 3β-HSD1 and 3β-HSD2 are regulated by multiple signalling pathways. Also, IL-4 was identified as an anti-inflammatory agent in hOSE with putative therapeutic benefit in malignancy.